1. What is an avg salary for a person with 7 yrs exp in java, looking for a position as an Architect/Team Leader/Senior Developer etc..
Check some job agencies websites and they give average salary etc. For a senior developer to architect the range would from $80k - $150.
2. What are the cities that I should look for, what abt Melbourne ?
In general Sydney is the where most of the banking and finance jobs are. Melbourne is mostly engineering jobs. Brisbane and Canberra are doing well at the moment, mostly government jobs.
3. Cost of living(with family) ?
If you live in Sydney, it not the cheapest state. I heard recently the median cost of rent is around $300 a week; house prices are around $350k-$450k, if you want something nice maybe above $500k; fuel price is around $1.30 - $1.50 a litre. In general things are going up not down.
4. Approx what % of salary is taxed ?
Have a look at the ato website to give you details on the specific tax rates ATO
. In general you should be taxed around 40%, unless you earn above 150k you will be taxed 45%
Hope it helps,